The Cornish or West Country Litany, asked to be delivered “From ghoulies and ghosties and long-leggety beasties/And things that go bump in the night.”

Hallowe’en may now be associated with “things that go bump in the night,” but prior to the Christianization of Celtic Europe, it was a major holiday when the spirits of the dead were said to roam the earth and party with the living, and was the most important event on the Celtic calendar, marking the end of the old and the commencement of the New Year. The Celts believed in trickster fairies, and, like the mythical beings, on the evening of October 31 would go from house to house to beg for treats. If treats weren’t provided, a practical joke was played on the homeowner — the “trick or treat” of today’s Hallowe’en.

The advent of Christianity signalled the end of a feast to the dead and commenced the celebration of the blessed dead in God’s eyes; thus All Hallow’s Eve, the day before All Soul’s Day. And since the Church believed in the existence of Heaven and Hell, instead of fairies and grateful dead wandering the earth, demons and benevolent spirits walked the world to taunt humans. This prompted the prayer for protection from “things that go bump in the night.”

During the Medieval period, people commonly imagined they were being plagued by demons sent by Satan to test their faith. Today, demons may occasionally be reported, but it is more likely the thing that “goes bump in the night” is a UFO.

“Once you turn on the imagination, all things are possible,” said Robert Baker, a professor emeritus of psychology at the University of Kentucky, during a 1994 Seattle conference entitled The Psychology of Belief. The conference delved into such “beasties” as UFOs, alien abductions and the controversy surrounding recovered memory. At the same conference, James Alcock, a professor of psychology at Glendon College, York University, said our minds “take in information from the environment, combine it with aspects of memory, shape it to satisfy certain needs, and produce a belief that may or may not have anything to do with reality.” He called it “magical thinking.”

“We must always, to some degree, be suspicious of our own experience. We must never take it as the arbiter of truth.”

Since 1994, more extensive research has been done on how the mind works. The research indicates sometimes our beliefs include items that are completely bogus, but are repeated over and over again until we no longer doubt their veracity. The explanation for believing in the bogus boils down to how our brains function, according to the recent article, Human Memory Routinely Makes Fact from Fiction, by science reporter Scott LaFee, which appeared in the San Diego Union Tribune. “Among the quirkier aspects of human cognition is the way our brains store and recall memories, frequently converting rumours, falsities and opinions into perceived, recollected facts,” wrote LaFee.

“Everybody does it,” said Sam Wang, an associate professor of molecular biology and neuroscience at Princeton University. “Memory formation and retrieval isn’t like writing down something on a piece of paper. Memories drift and change, and things we may have once doubted, we no longer do.”

New facts are first stored in the hippocampus, a pair of pinkie-sized structures deep within the brain, but they don’t stay there permanently or unchanged, according to Wang.

“As we recall facts, said Wang, our brains reprocess them, collate new information, reinterpret the result, then re-store them as new and ‘improved memories.’ Over time, much-used facts are transferred from the hippocampus to the cerebral cortex, the grayish many-folded outer layer of the brain. Somewhere along the way, Wang explained, these facts may be separated from the context in which they were first learned.”

“Reports of things like the Loch Ness monster or of UFOs are believed because the fantastic is fascinating and more dramatically interesting than the facts of ordinary life,” Karl Scheibe, an emeritus professor of psychology at Wesleyan University in Connecticut, told LaFee. He said it is easier to believe the unbelievable than remember it cannot be believed.

We all have run across a person who tells us something that he or she firmly believes is fact, when we know it’s baloney and have the information to disprove the assertion. Regardless of how well we explain that the original assertion is false, the believer can never be convinced that he or she is wrong.

In this case, the original information is absorbed without context or accompanying attribution — the term used is “source amnesia.” If a person remembers the information and source, then he or she has the ability to reason out whether the source is reliable. Thinking critically is one of the best ways to avoid assimilating false information and creating false memories.

The power of suggestion is extremely strong for some people. In a report from LiveScience, Richard McNally, a clinical psychologist at Harvard University, found that self-proclaimed alien abductees are twice as likely to commit source-monitoring memory errors.

“It might be harder to discriminate between a vivid image that you’d generate yourself and the memory of a perception of something you actually saw,” he said. Once people make this kind of mistake, they stick to their guns for spiritual reasons, he added. “We suspect that this might be kind of a psychological buffering mechanism against the fear of death.”

People prone to believe they have been abducted by aliens have been shown to have experienced “sleep paralysis,” which is correlated with the REM (Rapid Eye Movement) cycle, according to McNally. For an unlucky handful of people, this paralysis is accompanied by horrifying visual and auditory hallucinations — bright lights, a sense of choking and the conviction an intruder is present. The Japanese call it kanashibari, a devil sleeping on a hapless victim’s chest; the Chinese call it gui ya, or ghost pressure.

Consider a crime scene. Police know that when they interview witnesses after the fact, the stories told often conflict. Some police enforcement agencies regard eyewitness accounts as the most unreliable of sources. Police have to be able to sift through what is believable and what is actually false memory.

The Celts believed in trickster fairies appearing on Hallowe’en, while when we express a belief in “things that go bump in the night,” we are really being tricked by our brains.